Vehicle operating costs per mile are an ever-increasing concern of the automotive industry and the trucking segments of the transportation industry. Reducing vehicle fuel consumption is one way to improve vehicle operating costs. Manufacturers of major drive-train components, such as engines, transmissions, and axles are continually developing new technologies and refining existing technologies to reduce fuel consumption. Some examples of these developments include hybrid engine systems that internally generate more power per fixed volume of fuel, using mechanical components with lower frictional attributes, reducing exhaust system back pressure, and improving the manufacturing tolerances of transmission gear teeth.
Trucks utilizing automated mechanical transmissions (also referred to as automated manual transmissions or AMTs) depend on gear shifting logic or algorithms to determine the appropriate gear for a wide variety of conditions. Shift decisions may be based on balancing a variety of factors, including maximizing fuel efficiency, maximizing performance, and providing a desired driving experience.
In many driving situations, engine-generated power is not required at the wheels. In these coasting situations, some systems reduce fuel consumption by shifting a transmission to a neutral state, thus eliminating engine braking or any other frictional losses associated with components or systems positioned in the drive-train between the decoupled transmission and the engine, including components of the decoupled transmission. However, constant engine braking or continuous engine control is often required to maintain a safe distance between moving vehicles or to safely operate a vehicle in heavy traffic conditions, hilly regions, routes that cross railroad tracks, and during highway use with cruise control operation. The need for continuous engine control is even more important for trucks and other heavy vehicles, in which vehicle brakes are prone to overheating and failure when overused. In some jurisdictions, shifting the transmission to a neutral state while coasting downhill is illegal.